The objective of this research is to gain a more detailed understanding of the relationship between the structure of RNA and ribosomes and their function in protein synthesis. To this end several lines of investigation are being pursued. These include an examination of the interaction between ribosomal proteins and RNA covalently bound through the 3'-terminus to an agarose matrix. The interaction between ribosomal proteins of various origins and bacterial 5S RNA, tRNA and ribosomal RNA as well as with eukaryotic RNAs will be studied. A second approach to the objective involves investigating the molecular mechanism of the effects produced by the pyrimidine analogue 5-fluorouracil (FU) on the structure, function and synthesis of RNA. Our previous studies had shown that FU is incorporated into bacterial RNA and leads to the formation of abnormal ribosomal particles (FU-particles). To learn more about the function of ribosomal RNA (rRNA) and its role in ribosome structure, these altered ribosomes and their RNA and protein constituents will be characterized. Incorporation of FU into tRNA alters its structure and properties. Among other things the level of several minor nucleotide components is reduced. The physical-chemical properties of these modified tRNAs, both mixtures and individual species, and their ability to function in accepting amino acids and transferring them into polypeptides will be examined. Fluorine nmr studies on purified tRNA species will be initiated as a means of investigating the interaction of tRNA with various protein factors and with ribosomes. BIBLIOGRAPHIC REFERENCE: "Structural Requirements of tRNA for ppGpp Synthesis During the Stringent Response." G. Chinali, J. Ofengand, J. Horowitz and S. Chladek, Fed. Proc. 35, 1485 (1976).